Experiments on opto-electrically generated microfluidic vortices |
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Authors: | Aloke Kumar Stuart J Williams Steven T Wereley |
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Affiliation: | (1) Birck Nanotechnology Center and School of Mechanical Engineering, Purdue University, West Lafayette, IN 47907, USA |
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Abstract: | Strong microfluidic vortices are generated when a near-infrared (1,064 nm) laser beam is focused within a microchannel and
an alternating current (AC) electric field is simultaneously applied. The electric field is generated from a parallel-plate,
indium tin oxide (ITO) electrodes separated by 50 μm. We present the first μ-PIV analysis of the flow structure of such vortices.
The vortices exhibit a sink-type behavior in the plane normal to the electric field and the flow speeds are characterized
as a function of the electric field strength and biasing AC signal frequency. At a constant AC frequency of 100 kHz, the fluid
velocity increases as the square of the electric field strength. At constant electric field strength fluid velocity does not
change appreciably in the 30–50 kHz range and it decreases at larger frequencies (>1 MHz) until at approximately 5 MHz when
Brownian motion dominates the movement of the 300 nm μ-PIV tracer particles. Presence of strongly focused laser beams in an
interdigitated-electrode configuration can also lead to strong microfluidic vortices. When the center of the illumination
is focused in the middle of an electrode strip, particles experiencing negative dielectrophoresis are carried towards the
illumination and aggregate in this area. |
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Keywords: | MicroTAS Opto-electrostatic micro vortex Micropump Electrohydrodynamics Dielectrophoresis |
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